Beer : Health and Nutrition

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The Impact of Alcohol on Health 131
Such direct studies are important to underpin the much more prevalent investigations
that are based on surveys and questionnaires.
It will be appreciated that components of the diet, such as antioxidants, will only be
of bene t if they are demonstrated to enter the body and indeed reach the tissues that
they are to protect. The number of studies demonstrating a direct uptake of antioxidants
into the body is limited.
Bourne et al. (2000) showed that ferulic acid in alcohol-free beer (selected to maintain
the sobriety of test subjects) could be detected in the urine (Fig. 6.2). Comparable
results were observed for a series of polyphenolics (Walker & Baxter 2000). To reach
the kidney a material must be absorbed into the digestive system. While this is not an
a priori guarantee that the antioxidant reaches all of the tissues where it might have a
protective role, it does appear that all of the ferulic acid is absorbed by the body, suggesting
the ready availability of the substance in beer. By contrast, the absorption of
ferulic acid from tomatoes was only 11–25%. This is an important illustration of how the
food matrix can make a direct impact on the availability of a component. Just because
it is present in high quantities in a food, it does not necessarily mean that the food is a
better source of a material than another food in which it is present in lower quantities.
If questioned, most people would say that tomatoes are a healthier food than beer. In at
least one respect, though, this appears not necessarily to be the case.
It seems that the presence of alcohol stimulates the uptake of antioxidants into the
body (Ghiselli et al. 2000). After only one hour, a 17% increase in the measurable
antioxidant level (TAA) was observed in the volunteers’ blood.
The main category of substances discussed in the context of antioxidant potential of
red wines is the polyphenols (Frankel et al. 1993). Hertog et al. (1993) indicated that a
ferulic acid in urine (mg)
0
0 500 1000
time (minutes)
from beer
from tomatoes
Fig. 6.2 Uptake of ferulic acid from beer and tomatoes. (Redrawn from Bourne et al. 2000.)